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What is the torque about the origin on a jar of jalapeño peppers located at coordinates \((3.0 \mathrm{~m},-2.0 \mathrm{~m}, 4.0 \mathrm{~m})\) due to (a) force \(\vec{F}_{A}=(3.0 \mathrm{~N}) \hat{\mathrm{i}}-(4.0 \mathrm{~N}) \hat{\mathrm{j}}+(5.0 \mathrm{~N}) \hat{\mathrm{k}},(\mathrm{b})\) force \(\vec{F}_{B}=\) \((-3.0 \mathrm{~N}) \hat{\mathrm{i}}-(4.0 \mathrm{~N}) \hat{\mathrm{j}}-(5.0 \mathrm{~N}) \hat{\mathrm{k}}\), and \((\mathrm{c})\) the vector sum of \(\vec{F}_{A}\) and \(\vec{F}_{B} ?\) (d) Repeat part (c) about a point with coordinates \((3.0 \mathrm{~m},\), \(2.0 \mathrm{~m}, 4.0 \mathrm{~m}\) ) instead of about the origin.

Short Answer

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Step by step solution

01

Define the torque formula

Use the formula for torque \( \vec{\tau} = \vec{r} \times \vec{F} \), where \( \vec{r} \) is the position vector and \( \vec{F} \) is the force vector.
02

Calculate cross product for part (a)

Given the position vector \( \vec{r} = (3.0 \mathrm{~m}, -2.0 \mathrm{~m}, 4.0 \mathrm{~m}) \) and force vector \( \vec{F}_{A} = (3.0 \mathrm{~N}) \hat{\mathrm{i}} - (4.0 \mathrm{~N}) \hat{\mathrm{j}} + (5.0 \mathrm{~N}) \hat{\mathrm{k}} \), use the determinant to find the cross product: \

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Cross Product
The cross product of two vectors is a fundamental operation in vector algebra. It results in a vector that is perpendicular to the plane formed by the initial vectors. The formula for the cross product is:

\[ \text{Torque} \rightarrow \tau = \textbf{r} \times \textbf{F} \]

This means you multiply two vectors, the position vector (\textbf{r}) and the force vector (\textbf{F}), using a specific operation that determines the direction and magnitude of the resulting torque vector.

For example, if you have vectors \textbf{A} = \[a_1 \textbf{i} + a_2 \textbf{j} + a_3 \textbf{k}\] and \textbf{B} = \[b_1 \textbf{i} + b_2 \textbf{j} + b_3 \textbf{k}\], their cross product \textbf{A} × \textbf{B} is calculated as follows:
\[ \textbf{A} \times \textbf{B} = \begin{vmatrix} \textbf{i} & \textbf{j} & \textbf{k} \ a_1 & a_2 & a_3 \ b_1 & b_2 & b_3 \right) \].
This determinant calculation will give you a vector that indicates the direction and magnitude of the torque.
Position Vector
A position vector is a vector that extends from the origin of a coordinate system to the position of a point in space. It is typically denoted by \(\textbf{r}\) and expressed in the form:

\[ \textbf{r} = x \textbf{i} + y \textbf{j} + z \textbf{k} \]

In our problem, the position vector (\textbf{r}) of the jar of jalapeño peppers is given as:
\[ \textbf{r} = 3.0 \text{ m} \textbf{i} - 2.0 \text{ m} \textbf{j} + 4.0 \text{ m} \textbf{k} \]

This vector points from the origin to the coordinates (3.0 m, -2.0 m, 4.0 m). The position vector is crucial in determining the torque because it defines the relative location of the point where the force applies.
Force Vector
A force vector represents the force applied to an object, defined by its magnitude and direction. It is typically expressed in vector form as:

\[ \textbf{F} = F_x \textbf{i} + F_y \textbf{j} + F_z \textbf{k} \]

For example, for the given forces in the problem, we have:
1. Force \(\textbf{F}_A\): \[ \textbf{F}_A = 3.0 \text{ N} \textbf{i} - 4.0 \text{ N} \textbf{j} + 5.0 \text{ N} \textbf{k} \]
2. Force \(\textbf{F}_B\): \[ \textbf{F}_B = -3.0 \text{ N} \textbf{i} - 4.0 \text{ N} \textbf{j} - 5.0 \text{ N} \textbf{k} \]

The direction in which the force vector points determines how the object will move or rotate, while the magnitude (denoted by the values along \textbf{i}, \textbf{j}, and \textbf{k}) determines the strength of the force. These vectors are essential in calculating the torque using the cross product.

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Most popular questions from this chapter

A \(140 \mathrm{~kg}\) hoop rolls along a horizontal floor so that its center of mass has a speed of \(0.150 \mathrm{~m} / \mathrm{s}\). How much work must be done on the hoop to stop it?

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